1. Field of the Invention
This invention relates to artificial lens structures for implantation in the human eye, and particularly to an artificial lens for intraocular implantation in the posterior chamber of the eye.
2. Description of the Prior Art
Prior art relating to this invention is believed to be found in Class 3, sub-class 13; Class 128, sub-class 76.5; and Class 351, sub-classes 40 and 160. A search through these classes and sub-classes has revealed the existence of the following nine U.S. Pat. Nos.: 3,458,870; 3,673,616; 3,711,870; 3,866,249; 3,906,551; 3,913,148; 3,925,825; 3,971,073 and 4,079,470.
It is noted that of these nine patents, there are only three that relate to lens structures adapted for implantation in the posterior chamber of the eye. Those three are U.S. Pat. Nos. 3,711,870; 3,866,249 and 3,913,148. Referring specifically to U.S. Pat. No. 3,711,870 this patent teaches the implantation of an artificial lens in the posterior chamber of the eye but does so by providing the lens with a resilient peripheral flange that is then sutured to the ciliary muscle to position the lens radially and axially in the eye. U.S. Pat. No. 3,866,249 also relates to a posterior chamber artificial intraocular lens structure, and also provides a peripheral flange surrounding the optical zone of the lens, with the peripheral flange being provided in turn with a plurality of prongs projecting from the lens structure that are adapted to be pushed through the stroma tissue of the iris which has the unique property of not healing when damaged by a tear or a puncture. U.S. Pat. No. 3,913,148 presents the concept of implantation of intraocular lens structure in the posterior chamber of the eye and provides a plurality of clips mounted to the central portion of the lens and extending outwardly from the face and toward the outer periphery. The clips are movable from an iris-receiving position to an iris-engaging position. In one embodiment disclosed by this patent the clips are resilient and their inherent resilience effects movement of the clips to bind the iris to the anterior surface of the lens structure, while in another embodiment, the clips are malleable and are physically moved into engaging position with the face of the iris tissue in the anterior chamber of the eye after insertion of the lens.
All of the remaining patents noted above, with the exception of the three discussed in detail, relate to intraocular lens structures that are specifically designed to be received in the anterior chamber of the eye rather than in the posterior chamber of the eye. Referring specifically to this latter group of patents, it is noted that U.S. Pat. No. 3,458,870 relates to an artificial corneal implant including a lens structure. The thrust of this patent is to the correction of corneal opacification by the insertion between surgically established anterior and posterior corneal layers of an artificial corneal implant one portion of which includes a lens structure. The patent does not teach the concept of insertion of a primary lens structure in the posterior chamber of the eye to replace the natural lens normally found in that position.
U.S. Pat. No. 2,673,616 is believed to be known in the art as the Binkhorst-Federov ocular lens, Mr. Binkhorst having written a paper for the British Journal of Opthomology, Volume 51 (1967), Pages 767-77. The lens structure taught by this patent is designed as an anterior chamber lens structure and includes a pair of oppositely disposed loops anchored to the backside of the lens at points spaced inwardly from the outer periphery of the lens, the rounded loops extending radially outwardly beyond the periphery of the lens. Additionally, the lens incorporates radially extending rods the inner ends of which are secured to the outer periphery of the lens so that the rods lie in a substantially median plane of the lens. When implanted, the two oppositely extending loops lie behind the iris in the posterior chamber of the eye while the three rods are positioned forwardly of the iris in the anterior chamber of the eye. One of the disadvantages of this lens is that the lens must be held in place by constriction of the pupil, thus requiring that the patient take miotic eye drops daily to maintain the lens in position. Obviously, should the pupils dialate for any reason, the lens can subluxate and require reinsertion.
U.S. Pat. No. 3,906,551 relates to an intraocular lens system including a lens body having a pair of oppositely projecting support loops extending radially beyond the periphery of the lens structure. Additionally, the lens body is provided with a haptic rim extending radially from its outer periphery and with a pair of apertures symetrically placed with respect to the loops and overlying the junction of the haptic rim and the outer periphery of the lens. The apertures are stated to be for the purpose of permitting the lens structure to be sutured to the iris.
U.S. Pat. No. 3,925,825 also relates to a lens structure for implantation in the anterior chamber of the eye rather than in the posterior chamber thereof. Briefly, the structure includes an optical lens member mechanically surrounded and enclosed by a support structure including a "wire" rim mounted on the periphery of the lens structure.
U.S. Pat. No. 3,971,073 teaches the concept of an intraocular lens structure adapted for implantation in the anterior chamber of the eye rather than posteriorly to the iris. The structure includes supporting loops extending radially from the lens structure, all of which project from the flat or planar side of the lens, the loops being axially offset from one another on the posterior side of the lens so as to provide a space therebetween for receiving the iris.
U.S. Pat. No. 4,079,470 relates to an anterior chamber lens incorporating a support structure similar to the support structure taught by U.S. Pat. No. 3,673,616 discussed above, but teaching the concept of incorporating a lens formed of a low density material or synthetic crystals such as corundum, sapphire, zircon, ruby, strontium titanate, diamond, anatase and rutile.
From the foregoing it will be clear that in this particular art even minute mechanical modifications in the construction of lens structures, whether they be for anterior or posterior implantation make a considerable and sometimes crucial difference as to the effectiveness of the lens. One of the problems appears to be the desirability of placing the artificial lens in as close to the position of the original natural lens as possible, which of course eliminates consideration of artificial lenses positioned in the anterior chamber of the eye. Another problem is preventing irritation of the inner surface of the cornea by impingement thereon of structure that might be used to fasten the artificial lens to the iris tissue.
Accordingly, it is one of the primary objects of this invention to provide an artificial intraocular lens structure that avoids these problems.
A problem that is particularly important with respect to both anterior chamber and posterior chamber lenses is the risk of damage that might result from the dislocation or subluxation of the lens structure at some time after implantation. Such dislocation may occur from violent body contact, from a blow to the eye, or from inordinate pressure exerted on the eye. In the case of a posterior chamber lens such as the one forming the subject matter of this invention, the problem is minimized by the construction of the lens forming the subject matter of this invention.
The invention possesses other objects and features of advantage, some of which, with the foregoing, will be apparent from the following description and the drawings. It is to be understood however that the invention is not limited to the embodiments illustrated and described since the invention may be embodied in various forms within the scope of the appended claims.